1. Field of the Invention
The present invention relates to wireless networks, and, more particularly, to assigning time slots within wireless networks.
2. Description of the Related Art
Typically, automotive body domain applications such as seat control, window lift, mirror adjustment, and light control are distributed over the entire car and are interconnected via field bus communication systems. Current architectures have grown fast over the last decades as more and more convenience functions are introduced to the automotive industry.
The current architectures are hierarchical architectures in which several electronic control units (ECUs) are located near the body domain applications such as the seat ECU under the seat, the door ECU within the door, the ECU for rear light control in the trunk of the car, etc. All these ECUs are interconnected over field bus systems such as the “controller area network” (CAN) field bus, and these ECUs form the first hierarchy of the system. This field bus of the first hierarchy can also be regarded as the backbone network of the body domain.
The ECUs usually consist of a microcontroller and so-called peripheral drivers such as semiconductor switches, relays, signal amplifiers, etc. From the ECUs, several point-to-point wires connect to the peripherals of the applications like the motors (window, lift, seat adjustment), pushbutton panels, heating elements, sensors, etc. The number of these peripherals is constantly increasing for each application. For example, fifteen years ago a comfort seat had only three motors to move the seat forward and backward, to adjust the backrest, and to adjust the height. However, current seats may have about fifteen motors for additional functions such as air ventilation, massage functions, etc.
In order to connect the peripherals, a large number of cables may be necessary, which increases the complexity of the cable harness, increases the weight of the car, and increases the costs of the car. The increase in the number of cables may also lead to reliability problems in areas where the cable harness is mounted on moveable parts such as the side mirror, doors, seat, etc. Hence, in known architectures a second hierarchy order in the form of a so-called “subsystem” may be provided. Subsystems may have their own wired communication network which is usually a low cost communication system such as a local interconnect network (LIN). In contrast to the backbone, these networks are usually master-slave systems and not multimaster systems. The ECU that has access to the backbone is usually the master and the peripherals are the slaves. The ECU is also the gateway between the backbone and the subsystem.
The state-of-the-art of automotive electronics is progressing rapidly and it is projected that electronics alone will make up forty percent of the total cost of future cars. All these electronic units in the vehicle are connected through different bus systems depending on the application requirements. Typically, a hierarchical body domain automotive network 100 (FIG. 1) consists of several sub-networks, such as sub-networks 112, 114, connected together to form a larger network. The sub-networks technology being used is, for instance, a Local Interconnect Network (LIN). Each sub-network consists of a gateway node or ECU 116 and some sensor/actuator nodes 118. Network 100 may include a wired backbone 120 compatible with a Controller Area Network (CAN), FlexRay, Ethernet, etc. Network 100 may also include a body computer 124 and wired communication links 122 compatible with a CAN, Local Interconnect Network (LIN), FlexRay, Ethernet, etc.
ECUs 116 may be interconnected with each other over wired backbone field bus systems 120. Peripherals 118 may be directly connected to ECUs 116. Peripherals 118 may include tiny electronics and may communicate over another field bus with the main ECU. Thus, ECUs 116 may function in such architecture as gateways which communicate on one end with network backbone 120 and on the other end with the local sub-networks. The sub-networks may be organized in master-slave relationships in which the ECU is the master for the distributed tiny electronics in peripherals 118.
A problem associated with the architecture of FIG. 1 is that is that it has poor reliability. For example, if one of the ECUs fails, then the entire associated subsystem is no longer able to operate. Another problem is that there may be long time delays for end-to-end communication as gateways become bottlenecks. Yet another problem is that modularity and scalability are limited by the underlying sub-network systems.
Although implementing at least some of the architecture of FIG. 1 wirelessly has been considered, wireless communication is unpredictable and hence raises questions about the responsiveness of such a system as compared to wired networks. Another challenge is in avoiding interference between the wireless signals of adjacent systems, such as in adjacent automobiles. Yet another challenge is in taking advantage of the flexibility in communication methods that is afforded by wireless systems.
What is neither disclosed nor suggested in the art are methods of wireless communication that may avoid the above-mentioned problems, that more fully take advantage of the flexibility of wireless communication, and that provide more robust network performance.